src/getargs.c

   1 /* Parse command line arguments for Bison.
   2
   3    Copyright (C) 1984, 1986, 1989, 1992, 2000-2013 Free Software
   4    Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    This program is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "system.h"
  23 #include "output.h"
  24
  25 #include <argmatch.h>
  26 #include <c-strcase.h>
  27 #include <configmake.h>
  28 #include <error.h>
  29 #include <getopt.h>
  30 #include <progname.h>
  31
  32 #include "complain.h"
  33 #include "files.h"
  34 #include "getargs.h"
  35 #include "muscle-tab.h"
  36 #include "quote.h"
  37 #include "uniqstr.h"
  38
  39 bool defines_flag;
  40 bool graph_flag;
  41 bool xml_flag;
  42 bool no_lines_flag;
  43 bool token_table_flag;
  44 bool yacc_flag; /* for -y */
  45
  46 bool nondeterministic_parser = false;
  47 bool glr_parser = false;
  48
  49 int feature_flag = feature_caret;
  50 int report_flag = report_none;
  51 int trace_flag = trace_none;
  52
  53 static struct bison_language const valid_languages[] = {
  54   { "c", "c-skel.m4", ".c", ".h", true },
  55   { "c++", "c++-skel.m4", ".cc", ".hh", true },
  56   { "java", "java-skel.m4", ".java", ".java", false },
  57   { "", "", "", "", false }
  58 };
  59
  60 int skeleton_prio = default_prio;
  61 const char *skeleton = NULL;
  62 int language_prio = default_prio;
  63 struct bison_language const *language = &valid_languages[0];
  64 const char *include = NULL;
  65
  66 /** Decode an option's key.
  67  *
  68  *  \param option   option being decoded.
  69  *  \param keys     array of valid subarguments.
  70  *  \param values   array of corresponding (int) values.
  71  *  \param all      the all value.
  72  *  \param flags    the flags to update
  73  *  \param arg      the subarguments to decode.
  74  *                  If null, then activate all the flags.
  75  *  \param no       length of the potential "no-" prefix.
  76  *                  Can be 0 or 3. If 3, negate the action of the subargument.
  77  *
  78  *  If VALUE != 0 then KEY sets flags and no-KEY clears them.
  79  *  If VALUE == 0 then KEY clears all flags from \c all and no-KEY sets all
  80  *  flags from \c all.  Thus no-none = all and no-all = none.
  81  */
  82 static void
  83 flag_argmatch (const char *option,
  84                const char * const keys[], const int values[],
  85                int all, int *flags, char *arg, size_t no)
  86 {
  87   int value = 0;
  88   value = XARGMATCH (option, arg + no, keys, values);
  89
  90   if (value)
  91     {
  92       if (no)
  93         *flags &= ~value;
  94       else
  95         *flags |= value;
  96     }
  97   else
  98     {
  99       if (no)
 100         *flags |= all;
 101       else
 102         *flags &= ~all;
 103     }
 104 }
 105
 106 /** Decode an option's set of keys.
 107  *
 108  *  \param option   option being decoded.
 109  *  \param keys     array of valid subarguments.
 110  *  \param values   array of corresponding (int) values.
 111  *  \param all      the all value.
 112  *  \param flags    the flags to update
 113  *  \param args     comma separated list of effective subarguments to decode.
 114  *                  If 0, then activate all the flags.
 115  */
 116 static void
 117 flags_argmatch (const char *option,
 118                 const char * const keys[], const int values[],
 119                 int all, int *flags, char *args)
 120 {
 121   if (args)
 122     for (args = strtok (args, ","); args; args = strtok (NULL, ","))
 123       {
 124         size_t no = STRPREFIX_LIT ("no-", args) ? 3 : 0;
 125         flag_argmatch (option, keys,
 126                        values, all, flags, args, no);
 127       }
 128   else
 129     *flags |= all;
 130 }
 131
 132
 133 /** Decode a set of sub arguments.
 134  *
 135  *  \param FlagName  the flag familly to update.
 136  *  \param Args      the effective sub arguments to decode.
 137  *  \param All       the "all" value.
 138  *
 139  *  \arg FlagName_args   the list of keys.
 140  *  \arg FlagName_types  the list of values.
 141  *  \arg FlagName_flag   the flag to update.
 142  */
 143 #define FLAGS_ARGMATCH(FlagName, Args, All)                             \
 144   flags_argmatch ("--" #FlagName, FlagName ## _args, FlagName ## _types, \
 145                   All, &FlagName ## _flag, Args)
 146
 147
 148 /*----------------------.
 149 | --report's handling.  |
 150 `----------------------*/
 151
 152 static const char * const report_args[] =
 153 {
 154   /* In a series of synonyms, present the most meaningful first, so
 155      that argmatch_valid be more readable.  */
 156   "none",
 157   "state", "states",
 158   "itemset", "itemsets",
 159   "lookahead", "lookaheads", "look-ahead",
 160   "solved",
 161   "all",
 162   0
 163 };
 164
 165 static const int report_types[] =
 166 {
 167   report_none,
 168   report_states, report_states,
 169   report_states | report_itemsets, report_states | report_itemsets,
 170   report_states | report_lookahead_tokens,
 171   report_states | report_lookahead_tokens,
 172   report_states | report_lookahead_tokens,
 173   report_states | report_solved_conflicts,
 174   report_all
 175 };
 176
 177 ARGMATCH_VERIFY (report_args, report_types);
 178
 179
 180 /*---------------------.
 181 | --trace's handling.  |
 182 `---------------------*/
 183
 184 static const char * const trace_args[] =
 185 {
 186   "none       - no traces",
 187   "scan       - grammar scanner traces",
 188   "parse      - grammar parser traces",
 189   "automaton  - construction of the automaton",
 190   "bitsets    - use of bitsets",
 191   "grammar    - reading, reducing the grammar",
 192   "resource   - memory consumption (where available)",
 193   "sets       - grammar sets: firsts, nullable etc.",
 194   "muscles    - m4 definitions passed to the skeleton",
 195   "tools      - m4 invocation",
 196   "m4         - m4 traces",
 197   "skeleton   - skeleton postprocessing",
 198   "time       - time consumption",
 199   "ielr       - IELR conversion",
 200   "all        - all of the above",
 201   0
 202 };
 203
 204 static const int trace_types[] =
 205 {
 206   trace_none,
 207   trace_scan,
 208   trace_parse,
 209   trace_automaton,
 210   trace_bitsets,
 211   trace_grammar,
 212   trace_resource,
 213   trace_sets,
 214   trace_muscles,
 215   trace_tools,
 216   trace_m4,
 217   trace_skeleton,
 218   trace_time,
 219   trace_ielr,
 220   trace_all
 221 };
 222
 223 ARGMATCH_VERIFY (trace_args, trace_types);
 224
 225
 226 /*-----------------------.
 227 | --feature's handling.  |
 228 `-----------------------*/
 229
 230 static const char * const feature_args[] =
 231 {
 232   "none",
 233   "caret", "diagnostics-show-caret",
 234   "all",
 235   0
 236 };
 237
 238 static const int feature_types[] =
 239 {
 240   feature_none,
 241   feature_caret, feature_caret,
 242   feature_all
 243 };
 244
 245 ARGMATCH_VERIFY (feature_args, feature_types);
 246
 247 /*-------------------------------------------.
 248 | Display the help message and exit STATUS.  |
 249 `-------------------------------------------*/
 250
 251 static void usage (int) ATTRIBUTE_NORETURN;
 252
 253 static void
 254 usage (int status)
 255 {
 256   if (status != 0)
 257     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 258              program_name);
 259   else
 260     {
 261       /* For ../build-aux/cross-options.pl to work, use the format:
 262                 ^  -S, --long[=ARGS] (whitespace)
 263          A --long option is required.
 264          Otherwise, add exceptions to ../build-aux/cross-options.pl.  */
 265
 266       printf (_("Usage: %s [OPTION]... FILE\n"), program_name);
 267       fputs (_("\
 268 Generate a deterministic LR or generalized LR (GLR) parser employing\n\
 269 LALR(1), IELR(1), or canonical LR(1) parser tables.  IELR(1) and\n\
 270 canonical LR(1) support is experimental.\n\
 271 \n\
 272 "), stdout);
 273
 274       fputs (_("\
 275 Mandatory arguments to long options are mandatory for short options too.\n\
 276 "), stdout);
 277       fputs (_("\
 278 The same is true for optional arguments.\n\
 279 "), stdout);
 280
 281       fputs (_("\
 282 \n\
 283 Operation modes:\n\
 284   -h, --help                 display this help and exit\n\
 285   -V, --version              output version information and exit\n\
 286       --print-localedir      output directory containing locale-dependent data\n\
 287       --print-datadir        output directory containing skeletons and XSLT\n\
 288   -y, --yacc                 emulate POSIX Yacc\n\
 289   -W, --warnings[=CATEGORY]  report the warnings falling in CATEGORY\n\
 290   -f, --feature[=FEATURE]    activate miscellaneous features\n\
 291 \n\
 292 "), stdout);
 293
 294       fputs (_("\
 295 Parser:\n\
 296   -L, --language=LANGUAGE          specify the output programming language\n\
 297   -S, --skeleton=FILE              specify the skeleton to use\n\
 298   -t, --debug                      instrument the parser for tracing\n\
 299                                    same as `-Dparse.trace'\n\
 300       --locations                  enable location support\n\
 301   -D, --define=NAME[=VALUE]        similar to '%define NAME \"VALUE\"'\n\
 302   -F, --force-define=NAME[=VALUE]  override '%define NAME \"VALUE\"'\n\
 303   -p, --name-prefix=PREFIX         prepend PREFIX to the external symbols\n\
 304                                    deprecated by '-Dapi.prefix=PREFIX'\n\
 305   -l, --no-lines                   don't generate '#line' directives\n\
 306   -k, --token-table                include a table of token names\n\
 307 "), stdout);
 308       putc ('\n', stdout);
 309
 310       /* Keep -d and --defines separate so that ../build-aux/cross-options.pl
 311        * won't assume that -d also takes an argument.  */
 312       fputs (_("\
 313 Output:\n\
 314       --defines[=FILE]       also produce a header file\n\
 315   -d                         likewise but cannot specify FILE (for POSIX Yacc)\n\
 316   -r, --report=THINGS        also produce details on the automaton\n\
 317       --report-file=FILE     write report to FILE\n\
 318   -v, --verbose              same as `--report=state'\n\
 319   -b, --file-prefix=PREFIX   specify a PREFIX for output files\n\
 320   -o, --output=FILE          leave output to FILE\n\
 321   -g, --graph[=FILE]         also output a graph of the automaton\n\
 322   -x, --xml[=FILE]           also output an XML report of the automaton\n\
 323                              (the XML schema is experimental)\n\
 324 "), stdout);
 325       putc ('\n', stdout);
 326
 327       fputs (_("\
 328 Warning categories include:\n\
 329   `midrule-values'    unset or unused midrule values\n\
 330   `yacc'              incompatibilities with POSIX Yacc\n\
 331   `conflicts-sr'      S/R conflicts (enabled by default)\n\
 332   `conflicts-rr'      R/R conflicts (enabled by default)\n\
 333   `deprecated'        obsolete constructs\n\
 334   `precedence'        useless precedence and associativity\n\
 335   `other'             all other warnings (enabled by default)\n\
 336   `all'               all the warnings\n\
 337   `no-CATEGORY'       turn off warnings in CATEGORY\n\
 338   `none'              turn off all the warnings\n\
 339   `error[=CATEGORY]'  treat warnings as errors\n\
 340 "), stdout);
 341       putc ('\n', stdout);
 342
 343       fputs (_("\
 344 THINGS is a list of comma separated words that can include:\n\
 345   `state'        describe the states\n\
 346   `itemset'      complete the core item sets with their closure\n\
 347   `lookahead'    explicitly associate lookahead tokens to items\n\
 348   `solved'       describe shift/reduce conflicts solving\n\
 349   `all'          include all the above information\n\
 350   `none'         disable the report\n\
 351 "), stdout);
 352       putc ('\n', stdout);
 353
 354       fputs (_("\
 355 FEATURE is a list of comma separated words that can include:\n\
 356   `caret'        show errors with carets\n\
 357   `all'          all of the above\n\
 358   `none'         disable all of the above\n\
 359   "), stdout);
 360
 361       putc ('\n', stdout);
 362       printf (_("Report bugs to <%s>.\n"), PACKAGE_BUGREPORT);
 363       printf (_("%s home page: <%s>.\n"), PACKAGE_NAME, PACKAGE_URL);
 364       fputs (_("General help using GNU software: "
 365                "<http://www.gnu.org/gethelp/>.\n"),
 366              stdout);
 367       /* Don't output this redundant message for English locales.
 368          Note we still output for 'C' so that it gets included in the
 369          man page.  */
 370       const char *lc_messages = setlocale (LC_MESSAGES, NULL);
 371       if (lc_messages && !STREQ (lc_messages, "en_"))
 372         /* TRANSLATORS: Replace LANG_CODE in this URL with your language
 373            code <http://translationproject.org/team/LANG_CODE.html> to
 374            form one of the URLs at http://translationproject.org/team/.
 375            Otherwise, replace the entire URL with your translation team's
 376            email address.  */
 377         fputs (_("Report translation bugs to "
 378                  "<http://translationproject.org/team/>.\n"), stdout);
 379       fputs (_("For complete documentation, run: info bison.\n"), stdout);
 380     }
 381
 382   exit (status);
 383 }
 384
 385
 386 /*------------------------------.
 387 | Display the version message.  |
 388 `------------------------------*/
 389
 390 static void
 391 version (void)
 392 {
 393   /* Some efforts were made to ease the translators' task, please
 394      continue.  */
 395   printf (_("bison (GNU Bison) %s"), VERSION);
 396   putc ('\n', stdout);
 397   fputs (_("Written by Robert Corbett and Richard Stallman.\n"), stdout);
 398   putc ('\n', stdout);
 399
 400   fprintf (stdout,
 401            _("Copyright (C) %d Free Software Foundation, Inc.\n"),
 402            PACKAGE_COPYRIGHT_YEAR);
 403
 404   fputs (_("\
 405 This is free software; see the source for copying conditions.  There is NO\n\
 406 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\
 407 "),
 408          stdout);
 409 }
 410
 411
 412 /*-------------------------------------.
 413 | --skeleton and --language handling.  |
 414 `--------------------------------------*/
 415
 416 void
 417 skeleton_arg (char const *arg, int prio, location loc)
 418 {
 419   if (prio < skeleton_prio)
 420     {
 421       skeleton_prio = prio;
 422       skeleton = arg;
 423     }
 424   else if (prio == skeleton_prio)
 425     complain (&loc, complaint,
 426               _("multiple skeleton declarations are invalid"));
 427 }
 428
 429 void
 430 language_argmatch (char const *arg, int prio, location loc)
 431 {
 432   char const *msg;
 433
 434   if (prio < language_prio)
 435     {
 436       int i;
 437       for (i = 0; valid_languages[i].language[0]; i++)
 438         if (c_strcasecmp (arg, valid_languages[i].language) == 0)
 439           {
 440             language_prio = prio;
 441             language = &valid_languages[i];
 442             return;
 443           }
 444       msg = _("%s: invalid language");
 445     }
 446   else if (language_prio == prio)
 447     msg = _("multiple language declarations are invalid");
 448   else
 449     return;
 450
 451   complain (&loc, complaint, msg, quotearg_colon (arg));
 452 }
 453
 454 /*----------------------.
 455 | Process the options.  |
 456 `----------------------*/
 457
 458 /* Shorts options.
 459    Should be computed from long_options.  */
 460 static char const short_options[] =
 461   "D:"
 462   "F:"
 463   "L:"
 464   "S:"
 465   "T::"
 466   "V"
 467   "W::"
 468   "b:"
 469   "d"
 470   "f::"
 471   "e"
 472   "g::"
 473   "h"
 474   "k"
 475   "l"
 476   "n"
 477   "o:"
 478   "p:"
 479   "r:"
 480   "t"
 481   "v"
 482   "x::"
 483   "y"
 484   ;
 485
 486 /* Values for long options that do not have single-letter equivalents.  */
 487 enum
 488 {
 489   LOCATIONS_OPTION = CHAR_MAX + 1,
 490   PRINT_LOCALEDIR_OPTION,
 491   PRINT_DATADIR_OPTION,
 492   REPORT_FILE_OPTION
 493 };
 494
 495 static struct option const long_options[] =
 496 {
 497   /* Operation modes. */
 498   { "help",            no_argument,       0,   'h' },
 499   { "version",         no_argument,       0,   'V' },
 500   { "print-localedir", no_argument,       0,   PRINT_LOCALEDIR_OPTION },
 501   { "print-datadir",   no_argument,       0,   PRINT_DATADIR_OPTION   },
 502   { "warnings",        optional_argument, 0,   'W' },
 503
 504   /* Parser. */
 505   { "name-prefix",   required_argument,   0,   'p' },
 506   { "include",       required_argument,   0,   'I' },
 507
 508   /* Output. */
 509   { "file-prefix", required_argument,   0,   'b' },
 510   { "output",      required_argument,   0,   'o' },
 511   { "output-file", required_argument,   0,   'o' },
 512   { "graph",       optional_argument,   0,   'g' },
 513   { "xml",         optional_argument,   0,   'x' },
 514   { "report",      required_argument,   0,   'r' },
 515   { "report-file", required_argument,   0,   REPORT_FILE_OPTION },
 516   { "verbose",     no_argument,         0,   'v' },
 517
 518   /* Hidden. */
 519   { "trace",         optional_argument,   0,     'T' },
 520
 521   /* Output.  */
 522   { "defines",     optional_argument,   0,   'd' },
 523   { "feature",     optional_argument,   0,   'f' },
 524
 525   /* Operation modes.  */
 526   { "fixed-output-files", no_argument,  0,   'y' },
 527   { "yacc",               no_argument,  0,   'y' },
 528
 529   /* Parser.  */
 530   { "debug",          no_argument,               0,   't' },
 531   { "define",         required_argument,         0,   'D' },
 532   { "force-define",   required_argument,         0,   'F' },
 533   { "locations",      no_argument,               0, LOCATIONS_OPTION },
 534   { "no-lines",       no_argument,               0,   'l' },
 535   { "raw",            no_argument,               0,     0 },
 536   { "skeleton",       required_argument,         0,   'S' },
 537   { "language",       required_argument,         0,   'L' },
 538   { "token-table",    no_argument,               0,   'k' },
 539
 540   {0, 0, 0, 0}
 541 };
 542
 543 /* Under DOS, there is no difference on the case.  This can be
 544    troublesome when looking for `.tab' etc.  */
 545 #ifdef MSDOS
 546 # define AS_FILE_NAME(File) (strlwr (File), (File))
 547 #else
 548 # define AS_FILE_NAME(File) (File)
 549 #endif
 550
 551 /* Build a location for the current command line argument. */
 552 static
 553 location
 554 command_line_location (void)
 555 {
 556   location res;
 557   /* "<command line>" is used in GCC's messages about -D. */
 558   boundary_set (&res.start, uniqstr_new ("<command line>"), optind - 1, -1);
 559   res.end = res.start;
 560   return res;
 561 }
 562
 563
 564 void
 565 getargs (int argc, char *argv[])
 566 {
 567   int c;
 568
 569   while ((c = getopt_long (argc, argv, short_options, long_options, NULL))
 570          != -1)
 571     switch (c)
 572       {
 573         /* ASCII Sorting for short options (i.e., upper case then
 574            lower case), and then long-only options.  */
 575
 576       case 0:
 577         /* Certain long options cause getopt_long to return 0.  */
 578         break;
 579
 580       case 'D': /* -DNAME[=VALUE]. */
 581       case 'F': /* -FNAME[=VALUE]. */
 582         {
 583           char* name = optarg;
 584           char* value = strchr (optarg, '=');
 585           if (value)
 586             *value++ = 0;
 587           muscle_percent_define_insert (name, command_line_location (),
 588                                         value ? value : "",
 589                                         c == 'D' ? MUSCLE_PERCENT_DEFINE_D
 590                                                  : MUSCLE_PERCENT_DEFINE_F);
 591         }
 592         break;
 593
 594       case 'I':
 595         include = AS_FILE_NAME (optarg);
 596         break;
 597
 598       case 'L':
 599         language_argmatch (optarg, command_line_prio,
 600                            command_line_location ());
 601         break;
 602
 603       case 'S':
 604         skeleton_arg (AS_FILE_NAME (optarg), command_line_prio,
 605                       command_line_location ());
 606         break;
 607
 608       case 'T':
 609         FLAGS_ARGMATCH (trace, optarg, trace_all);
 610         break;
 611
 612       case 'V':
 613         version ();
 614         exit (EXIT_SUCCESS);
 615
 616       case 'f':
 617         FLAGS_ARGMATCH (feature, optarg, feature_all);
 618         break;
 619
 620       case 'W':
 621         warnings_argmatch (optarg);
 622         break;
 623
 624       case 'b':
 625         spec_file_prefix = AS_FILE_NAME (optarg);
 626         break;
 627
 628       case 'd':
 629         /* Here, the -d and --defines options are differentiated.  */
 630         defines_flag = true;
 631         if (optarg)
 632           {
 633             free (spec_defines_file);
 634             spec_defines_file = xstrdup (AS_FILE_NAME (optarg));
 635           }
 636         break;
 637
 638       case 'g':
 639         graph_flag = true;
 640         if (optarg)
 641           {
 642             free (spec_graph_file);
 643             spec_graph_file = xstrdup (AS_FILE_NAME (optarg));
 644           }
 645         break;
 646
 647       case 'h':
 648         usage (EXIT_SUCCESS);
 649
 650       case 'k':
 651         token_table_flag = true;
 652         break;
 653
 654       case 'l':
 655         no_lines_flag = true;
 656         break;
 657
 658       case 'o':
 659         spec_outfile = AS_FILE_NAME (optarg);
 660         break;
 661
 662       case 'p':
 663         spec_name_prefix = optarg;
 664         break;
 665
 666       case 'r':
 667         FLAGS_ARGMATCH (report, optarg, report_all);
 668         break;
 669
 670       case 't':
 671         muscle_percent_define_insert ("parse.trace",
 672                                       command_line_location (), "",
 673                                       MUSCLE_PERCENT_DEFINE_D);
 674         break;
 675
 676       case 'v':
 677         report_flag |= report_states;
 678         break;
 679
 680       case 'x':
 681         xml_flag = true;
 682         if (optarg)
 683           {
 684             free (spec_xml_file);
 685             spec_xml_file = xstrdup (AS_FILE_NAME (optarg));
 686           }
 687         break;
 688
 689       case 'y':
 690         warning_argmatch ("error=yacc", 0, 6);
 691         yacc_flag = true;
 692         break;
 693
 694       case LOCATIONS_OPTION:
 695         muscle_percent_define_ensure ("locations",
 696                                       command_line_location (), true);
 697         break;
 698
 699       case PRINT_LOCALEDIR_OPTION:
 700         printf ("%s\n", LOCALEDIR);
 701         exit (EXIT_SUCCESS);
 702
 703       case PRINT_DATADIR_OPTION:
 704         printf ("%s\n", pkgdatadir ());
 705         exit (EXIT_SUCCESS);
 706
 707       case REPORT_FILE_OPTION:
 708         free (spec_verbose_file);
 709         spec_verbose_file = xstrdup (AS_FILE_NAME (optarg));
 710         break;
 711
 712       default:
 713         usage (EXIT_FAILURE);
 714       }
 715
 716   if (argc - optind != 1)
 717     {
 718       if (argc - optind < 1)
 719         error (0, 0, _("%s: missing operand"), quotearg_colon (argv[argc - 1]));
 720       else
 721         error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
 722       usage (EXIT_FAILURE);
 723     }
 724
 725   current_file = grammar_file = uniqstr_new (argv[optind]);
 726   MUSCLE_INSERT_C_STRING ("file_name", grammar_file);
 727 }
 728
 729 void
 730 tr (char *s, char from, char to)
 731 {
 732   for (; *s; s++)
 733     if (*s == from)
 734       *s = to;
 735 }